Due to rapidly increasing traffic in optical communications in recent years, the transmitting capacity of presently used single-core optical fibers is approaching its limit. So, as a means to further expand the communication capacity, multi-core fibers in which a plurality of cores are formed in one fiber have been proposed. Use of multi-core fibers can suppress the laying cost of optical fibers and expand the transmission capacity.
If a multi-core fiber is used as a transmission path, each of the core parts of the multi-core fiber needs to be connected to another multi-core fiber, an optical element, or the like respectively to send and receive transmission signals.
As a connector using such a multi-core fiber, there is a connector in which positioning in rotational direction is considered for example (Patent Document 1).